Nuclear reactor system and method for operating the same

Abstract

A nuclear reactor system having a water-cooled reactor includes a reactor containment. A shielding pit inside the reactor containment has a lower region with an outlet opening formed therein. A reactor pressure vessel is disposed in the shielding pit. A moderating cell is disposed downstream of the outlet opening and has a device for slowing down and diverting a melt flowing through the outlet opening. A catch basin is disposed downstream of the moderating cell for receiving a melt and a supply of water. A method for operating a nuclear reactor system includes covering the bottom of the catch basin with water during normal operation of the reactor, and maintaining the water in the catch basin at a surface level being lower than the lowermost region of the bottom of the shielding pit.

We claim: 
     
       1. A nuclear reactor system having a water-cooled reactor, comprising: a reactor containment;   a shielding pit inside said reactor containment, said shielding pit having a lower region with an outlet opening formed therein;   a reactor pressure vessel disposed in said shielding pit;   a moderating cell disposed downstream of said outlet opening and laterally adjacent said shielding pit, said moderating cell having a device for slowing down and diverting a melt flowing through said outlet opening; and   a catch basin downstream of said moderating cell for receiving a melt, said catch basin being filled with a supply of water.   
     
     
       2. The nuclear reactor system according to claim 1, wherein said shielding pit has a bottom with a lowermost region, and said catch basin has a flat bottom being lower than said lowermost region. 
     
     
       3. The nuclear reactor system according to claim 1, wherein said shielding pit has a bottom with a lowermost region, said moderating cell has a bottom with a lowermost region, and said catch basin has a position and a size sufficient to hold a water supply for cooling the melt and coolant added from possible leakage, at a water surface level being maintained lower than said lowermost regions. 
     
     
       4. The nuclear reactor system according to claim 3, wherein said bottom of said catch basin is located at least one meter below said lowermost region of said bottom of said shielding pit. 
     
     
       5. The nuclear reactor system according to claim 4, wherein said bottom of said moderating cell is located at least one meter above said bottom of said catch basin. 
     
     
       6. The nuclear reactor system according to claim 2, wherein said bottom of said catch basin has an area of at least 100 m 2 . 
     
     
       7. The nuclear reactor system according to claim 1, wherein said moderating cell has an upper region with a pressure relief opening formed therein for steam. 
     
     
       8. The nuclear reactor system according to claim 1, wherein said shielding pit has an upper region with a pressure relief opening formed therein. 
     
     
       9. The nuclear reactor system according to claim 8, including an additional device associated with said pressure relief opening, for slowing down and deflecting a mixture of steam and melt emerging through said pressure relief opening. 
     
     
       10. The nuclear reactor system according to claim 1, wherein said shielding pit has a bottom with a slope descending in the direction of said outlet opening. 
     
     
       11. The nuclear reactor system according to claim 1, wherein said shielding pit and said moderating cell have bottoms and walls formed of concrete with a thickness of at least one meter. 
     
     
       12. The nuclear reactor system according to claim 1, wherein said catch basin is disposed inside said reactor containment. 
     
     
       13. A nuclear reactor system having a water-cooled reactor, comprising: reactor containment;   a shielding pit inside said reactor containment, said shielding pit having a lower region with an outlet opening formed therein;   a reactor pressure vessel disposed in said shielding pit;   a moderating cell disposed downstream of said outlet opening and laterally adjacent said shielding pit, said moderating cell having a device for slowing down and diverting a melt flowing through said outlet opening;   a catch basin downstream of said moderating cell for receiving a melt and a supply of water, said moderating cell having a bottom, and including a hollow chamber being disposed underneath said bottom of said moderating cell and being filled with water.   
     
     
       14. The nuclear reactor system according to claim 13, wherein said shielding pit has a bottom, and including a plurality of water-filled channels disposed underneath said bottom of said shielding pit. 
     
     
       15. A nuclear reactor system having a water-cooled reactor, comprising: a reactor containment;   a shielding pit inside said reactor containment, said shielding pit having a lower region with an outlet opening formed therein;   a reactor pressure vessel disposed in said shielding pit;   a moderating cell disposed downstream of said outlet opening and laterally adjacent said shielding pit, said moderating cell having a device for slowing down and diverting a melt flowing through said outlet opening;   a catch basin downstream of said moderating cell for receiving a melt and a supply of water, said catch basin having a bottom, and including a continuously curved drainage channel being disposed between said moderating cell and said catch basin, for discharging at a tangent onto said bottom of said catch basin.   
     
     
       16. The nuclear reactor system according to claim 15, wherein said bottom of said catch basin has a discharge region downstream of said outlet channel with a fire-proof lining. 
     
     
       17. The nuclear reactor system according to claim 1, including at least one other moderating cell, said moderating cells being disposed about the circumference of said shielding pit. 
     
     
       18. The nuclear reactor system according to claim 1, wherein said moderating cell annularly surrounds said shielding pit. 
     
     
       19. The nuclear reactor system according to claim 17, including other catch basins, said catch basins being disposed in a star pattern around said shielding pit. 
     
     
       20. The nuclear reactor system according to claim 18, including other catch basins, said catch basins being disposed in a star pattern around said shielding pit. 
     
     
       21. A method for operating a nuclear reactor system including a water-cooled reactor having a reactor containment; a shielding pit inside the reactor containment, the shielding pit having a lower region with an outlet opening formed therein and a bottom with a lowermost region; a reactor pressure vessel disposed in the shielding pit; a moderating cell disposed downstream of the outlet opening and horizontally adjacent the lowermost region of the shielding pit, the moderating cell having a device for slowing down and diverting a melt flowing through the outlet opening; and a catch basin being disposed downstream of the moderating cell and having a bottom for receiving a melt and a supply of water, which comprises: covering the bottom of the catch basin with water during normal operation of the reactor, and maintaining the water in the catch basin at a surface level being lower than the lowermost region of the bottom of the shielding pit.